CN113396642A - Induction heating cooker - Google Patents

Abstract

The induction heating cooker of the present invention includes: a drive circuit that supplies a high-frequency current to each of a plurality of heating coils including an inner coil and an outer coil; each of the plurality of heating coils is switched to a conductive state and a non-conductive state; and a control device that determines the upper part of the inner peripheral coil when the inner peripheral coil is in a conductive state and the outer peripheral coil is in a non-conductive state The presence or absence of the object to be heated will stop the operation of the drive circuit when there is no object to be heated above the inner peripheral coil.

Description

Induction heating cooker

Technical Field

The present invention relates to an induction heating cooker having a plurality of coils.

Background

In a conventional induction heating cooker, a configuration has been proposed in which a current is supplied to a plurality of coils by a single inverter circuit. For example, in the induction heating cooker described in patent document 1, an arithmetic control circuit controls an inverter circuit so as to supply currents of at least two frequencies to a plurality of coils. The arithmetic control circuit calculates the ratio of the currents between the plurality of coils at each frequency based on the currents measured by the measuring circuit, and determines the size of the object to be heated based on the relative relationship between the ratios of the currents at the frequencies.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2006-310006

Disclosure of Invention

Problems to be solved by the invention

In the induction heating cooker described in patent document 1, the ratio of the currents in the plurality of coils at each frequency is calculated, and the load is determined based on the relative relationship between the ratios of the currents at the frequencies, so that it takes time to determine the load. Therefore, there are problems as follows: when there is no load on which the object to be heated is not placed, the load determination operation cannot be stopped promptly.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an induction heating cooker capable of quickly stopping a load determination operation in a no-load state in a configuration in which a plurality of heating coils are driven by one drive circuit.

Means for solving the problems

The induction heating cooker of the invention comprises: a plurality of heating coils including an inner circumferential coil disposed on an innermost circumferential side and an outer circumferential coil disposed on an outermost circumferential side; one drive circuit that supplies a high-frequency current to each of the plurality of heating coils; an opening/closing part that switches each of the plurality of heating coils to a conductive state in which the high-frequency current is supplied from the drive circuit and a non-conductive state in which the high-frequency current is not supplied; and a control device that controls operations of the drive circuit and the opening/closing member, wherein the control device determines whether or not an object to be heated is present above the inner peripheral coil when the inner peripheral coil is in a conductive state and the outer peripheral coil is in a non-conductive state, and stops the operation of the drive circuit when the object to be heated is not present above the inner peripheral coil.

ADVANTAGEOUS EFFECTS OF INVENTION

In the present invention, the control device determines the presence or absence of an object to be heated above the inner peripheral coil when the inner peripheral coil is in a conductive state and the outer peripheral coil is in a non-conductive state, and stops the operation of the drive circuit when there is no object to be heated above the inner peripheral coil. Therefore, in the configuration in which the plurality of heating coils are driven by one driving circuit, the load determination operation in the no-load state can be promptly stopped.

Drawings

Fig. 1 is an exploded perspective view showing an induction heating cooker according to embodiment 1.

Fig. 2 is a plan view showing a first induction heating member of an induction heating cooker according to embodiment 1.

Fig. 3 is a block diagram showing a configuration of an induction heating cooker according to embodiment 1.

Fig. 4 is a diagram showing a drive circuit of an induction heating cooker according to embodiment 1.

Fig. 5 is a flowchart showing a heating operation of the induction heating cooker of embodiment 1.

Fig. 6 is a load determination characteristic diagram based on the relationship between the coil current and the input current in the induction heating cooker according to embodiment 1.

Fig. 7 is a diagram showing an object to be heated of the composite body induction-heated by the induction heating cooker of embodiment 1.

Fig. 8 is a diagram showing a heating coil and an object to be heated in the induction heating cooker according to embodiment 1.

Fig. 9 is a diagram illustrating an operation state of the first opening/closing member and the second opening/closing member in the preheating mode of the induction heating cooker according to embodiment 1.

Fig. 10 is a diagram illustrating an operation state of the first opening/closing member and the second opening/closing member in the small-diameter heating operation of the induction heating cooker according to embodiment 1.

Fig. 11 is a diagram illustrating an operation state of the first opening/closing member and the second opening/closing member in the large-diameter heating operation of the induction heating cooker according to embodiment 1.

Fig. 12 is a diagram showing a structure of an opening and closing member in modification 1 of the induction heating cooker of embodiment 1.

Fig. 13 is a diagram showing a structure of an opening and closing member in modification 1 of the induction heating cooker of embodiment 1.

Fig. 14 is a plan view showing the first induction heating member in modification 2 of the induction heating cooker of embodiment 1.

Fig. 15 is a plan view showing a first induction heating member of an induction heating cooker according to embodiment 2.

Fig. 16 is a block diagram showing a configuration of an induction heating cooker according to embodiment 2.

Fig. 17 is a diagram showing a circuit configuration of an induction heating cooker according to embodiment 2.

Fig. 18 is a flowchart showing a heating operation of the induction heating cooker of embodiment 2.

Fig. 19 is a flowchart showing a heating operation of the induction heating cooker of embodiment 2.

Fig. 20 is a diagram showing a structure of an opening and closing member in modification 1 of the induction heating cooker of embodiment 2.

Fig. 21 is a diagram showing a structure of an opening/closing member in modification 1 of the induction heating cooker of embodiment 2.

Fig. 22 is a diagram showing a circuit configuration of an induction heating cooker according to embodiment 3.

Detailed Description

Embodiment 1.

Fig. 1 is an exploded perspective view showing an induction heating cooker according to embodiment 1.

As shown in fig. 1, a top plate 4 on which an object 5 to be heated such as a pan is placed is provided above the induction heating cooker 100. The top plate 4 is provided with a first induction heating port 1 and a second induction heating port 2 as heating ports for inductively heating the object 5. The first induction heating port 1 and the second induction heating port 2 are arranged side by side in the lateral direction on the front side of the top plate 4. In addition, induction heating cooker 100 according to embodiment 1 further includes third induction heating port 3 as a third heating port. The third induction heating port 3 is provided at the inner side of the first induction heating port 1 and the second induction heating port 2 and at the substantially central position in the lateral direction of the top plate 4.

Below each of first induction heating port 1, second induction heating port 2, and third induction heating port 3, there are provided first induction heating member 11, second induction heating member 12, and third induction heating member 13 that heat object 5 placed on the heating ports. Each heating member is constituted by a heating coil (see fig. 2).

The entire top plate 4 is made of a material that transmits infrared rays, such as heat-resistant tempered glass or crystallized glass. Further, a circular pot position display showing the approximate placement position of the pot is formed on the top plate 4 in accordance with the heating ranges of the first induction heating member 11, the second induction heating member 12, and the third induction heating member 13 by coating or printing of paint.

An operation unit 40 is provided on the front side of the top plate 4 as an input device for setting the power input and the cooking menu for heating the object 5 or the like by the first induction heating member 11, the second induction heating member 12, and the third induction heating member 13. The cooking menu includes a preheating mode, a convection mode, and a normal heating mode, which will be described later. In embodiment 1, the operation unit 40 is divided into an operation unit 40a, an operation unit 40b, and an operation unit 40c for each induction heating coil.

In addition, a display unit 41 for displaying the operating state of each induction heating coil, the input from the operation unit 40, the operation content, and the like is provided as a notification member in the vicinity of the operation unit 40. In embodiment 1, the display unit 41 is divided into a display unit 41a, a display unit 41b, and a display unit 41c for each induction heating coil.

The operation unit 40 and the display unit 41 are not particularly limited to those provided for each induction heating member or those provided for common use for each induction heating member as described above. Here, the operation unit 40 is configured by, for example, a mechanical switch such as a push switch or a tact switch, a touch switch that detects an input operation from a change in electrostatic capacitance of an electrode, or the like. The display unit 41 is configured by, for example, an LCD and an LED.

The operation unit 40 and the display unit 41 may be an operation display unit 43 integrally configured with each other. The operation display unit 43 is constituted by, for example, a touch panel in which touch switches are arranged on the upper surface of an LCD.

In addition, the LCD is an abbreviation of Liquid Crystal Device. In addition, the LED is an abbreviation of Light Emitting Diode (LED).

A drive circuit 50 and a control device 45 are provided inside the induction heating cooker 100. The drive circuit 50 supplies high-frequency power to the coils of the first induction heating member 11, the second induction heating member 12, and the third induction heating member 13. The controller 45 controls the operation of the entire induction heating cooker including the drive circuit 50.

High-frequency power is supplied to the first induction heating member 11, the second induction heating member 12, and the third induction heating member 13 by the drive circuit 50, whereby a high-frequency magnetic field is generated from the coil of each induction heating member. Further, the detailed structure of the drive circuit 50 will be described later.

The first induction heating member 11, the second induction heating member 12, and the third induction heating member 13 are configured as follows, for example. The first induction heating member 11, the second induction heating member 12, and the third induction heating member 13 have the same configuration. Therefore, the structure of the first induction heating member 11 is representatively described below.

Fig. 2 is a plan view showing a first induction heating member of an induction heating cooker according to embodiment 1.

The first induction heating member 11 is formed by concentrically disposing a plurality of annular heating coils having different diameters. In fig. 2, the first induction heating member 11 is shown as a double loop coil. The first induction heating member 11 has an inner coil 111 disposed at the center of the first induction heating port 1 and an outer coil 112 disposed on the outer periphery side of the inner coil 111. That is, the inner circumferential coil 111 is a heating coil disposed on the innermost circumference side among the plurality of heating coils constituting the first induction heating member 11. The outer circumferential coil 112 is a heating coil disposed on the outermost periphery side among the plurality of heating coils constituting the first induction heating member 11.

The inner coil 111 and the outer coil 112 are formed by winding a conductive wire made of a metal having an insulating coating. As the lead, for example, any metal such as copper or aluminum can be used. Further, the inner coil 111 and the outer coil 112 are wound with wires independently.

In the following description, the inner coil 111 and the outer coil 112 may be collectively referred to as coils.

Fig. 3 is a block diagram showing a configuration of an induction heating cooker according to embodiment 1.

As shown in fig. 3, the inner coil 111 and the outer coil 112 are electrically connected in series. The inner coil 111 and the outer coil 112 are driven and controlled by one drive circuit 50.

The opening/closing member 60 has a first opening/closing member 61 connected in parallel with the inner peripheral coil 111 and a second opening/closing member 62 connected in parallel with the outer peripheral coil 112. The first opening/closing member 61 switches the inner peripheral coil 111 between a conductive state in which a high-frequency current is supplied from the drive circuit 50 and a non-conductive state in which a high-frequency current is not supplied. The second opening/closing member 62 switches the outer circumferential coil 112 between a conductive state in which a high-frequency current is supplied from the drive circuit 50 and a non-conductive state in which a high-frequency current is not supplied. The first opening/closing member 61 and the second opening/closing member 62 are formed of, for example, a relay that opens and closes a contact switch in response to an electric signal or a switching element formed of a semiconductor material.

When the inner coil 111 is in the on state, a high-frequency current is supplied from the drive circuit 50 to the inner coil 111, thereby generating a high-frequency magnetic field from the inner coil 111. When the outer-periphery coil 112 is in the on state, a high-frequency current is supplied from the drive circuit 50 to the outer-periphery coil 112, thereby generating a high-frequency magnetic field from the outer-periphery coil 112.

The control device 45 is constituted by dedicated hardware or a CPU that executes a program stored in the memory 48. The control device 45 further includes a load determination unit 46, and the load determination unit 46 determines the presence or absence and the material of the object 5 placed above each of the inner and outer coils 111 and 112.

In addition, the CPU is an abbreviation of Central Processing Unit (CPU). The CPU is also referred to as a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, or a processor.

When the control device 45 is dedicated hardware, the control device 45 corresponds to, for example, a single circuit, a composite circuit, an ASIC, an FPGA, or a component in which these are combined. Each of the functional units realized by the control device 45 may be realized by separate hardware, or may be realized by one hardware.

In addition, the ASIC is an abbreviation of Application Specific Integrated Circuit (ASIC). In addition, the FPGA is an abbreviation of Field-Programmable Gate Array (FPGA).

When the control device 45 is a CPU, each function executed by the control device 45 is realized by software, firmware, or a combination of software and firmware. The software and firmware are described as programs and stored in the memory 48. The functions of the control device 45 are realized by causing the CPU to read and execute the program stored in the memory 48. Here, the memory 48 is a nonvolatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM, and an EEPROM.

Further, a part of the functions of the control device 45 may be implemented by dedicated hardware, and a part may be implemented by software or firmware.

Further, the RAM is an abbreviation of Random Access Memory (Random Access Memory). The ROM is an abbreviation for Read Only Memory (ROM). In addition, EPROM is an abbreviation for Erasable Programmable Read Only Memory (Erasable Read Only Memory). In addition, EEPROM is an abbreviation of Electrically Erasable Read-Only Memory (EEPROM).

Fig. 4 is a diagram showing a drive circuit of an induction heating cooker according to embodiment 1.

The drive circuit 50 is provided for each heating element, and the circuit configuration may be the same or may be changed for each heating element. In fig. 4, a driving circuit 50 that drives the first induction heating member 11 is illustrated.

As shown in fig. 4, the drive circuit 50 includes a dc power supply circuit 22, an inverter circuit 23, and a resonant capacitor 24. A resonant circuit including an inner coil 111, an outer coil 112, and a resonant capacitor 24 is connected to the drive circuit 50. As shown in fig. 4, the connection point between the driver circuit 50 and the resonant circuit is shown by a terminal a and a terminal B.

The dc power supply circuit 22 includes a diode bridge 22a, a reactor 22b, and a smoothing capacitor 22c, converts an ac voltage input from the ac power supply 21 into a dc voltage, and outputs the dc voltage to the inverter circuit 23.

The IGBT23a and the IGBT23b as switching elements in the inverter circuit 23 are connected in series with the output of the dc power supply circuit 22. The diode 23c and the diode 23d, which are flywheel diodes, in the inverter circuit 23 are connected in parallel to the IGBT23a and the IGBT23b, respectively. The inverter circuit 23 is a so-called half-bridge inverter having one branch (arm) in which two switching elements are connected in series.

The IGBT23a and the IGBT23b are driven to be turned on and off in accordance with a drive signal output from the control device 45. The control device 45 turns off the IGBT23b while turning on the IGBT23a, and turns on the IGBT23b while turning off the IGBT23a, and outputs a drive signal that is alternately turned on and off. Thus, the inverter circuit 23 converts the dc power output from the dc power supply circuit 22 into high-frequency ac power of about 20kHz to 100kHz, and supplies the power to the resonance circuit including the inner coil 111, the outer coil 112, and the resonance capacitor 24.

Resonant capacitor 24 is connected in series to inner coil 111 and outer coil 112. The resonance circuit including the inner coil 111, the outer coil 112, and the resonance capacitor 24 has a resonance frequency corresponding to the inductance of the inner coil 111 and the outer coil 112 and the capacitance of the resonance capacitor 24. Further, the inductance of the inner and outer coils 111 and 112 changes in accordance with the characteristics of the metal load when the object 5 as the metal load is magnetically coupled, and the resonance frequency of the resonance circuit changes in accordance with the change in the inductance.

With this configuration, a high-frequency current of about several tens of amperes flows through inner coil 111 in the on state. The object 5 to be heated placed on the top plate 4 directly above the inner peripheral coil 111 is inductively heated by high-frequency magnetic flux generated by high-frequency current flowing through the inner peripheral coil 111.

A high-frequency current of about several tens of amperes flows through outer circumferential coil 112 in the on state. The object 5 to be heated placed on the top plate 4 directly above the outer circumferential coil 112 is inductively heated by high-frequency magnetic flux generated by high-frequency current flowing through the outer circumferential coil 112.

The IGBT23a and the IGBT23b serving as switching elements are made of, for example, a semiconductor formed of silicon, but may be formed using a wide band gap semiconductor material such as silicon carbide or a gallium nitride material.

By using a wide bandgap semiconductor for the switching element, the conduction loss of the switching element can be reduced. Further, since heat dissipation from the drive circuit 50 is good even when the drive frequency is set to a high frequency, that is, the switch is set to a high speed, the heat dissipation fins of the drive circuit 50 can be made small, and the drive circuit 50 can be made small and low in cost.

The input current detection means 25a is constituted by, for example, a current sensor, detects a current input from the ac power supply 21 to the drive circuit 50, and outputs a voltage signal corresponding to the input current value to the control device 45.

Coil current detection unit 25b is connected to a resonance circuit including inner coil 111, outer coil 112, and resonance capacitor 24. The coil current detection unit 25b is constituted by, for example, a current sensor, detects currents flowing through the inner coil 111 and the outer coil 112, and outputs a voltage signal corresponding to a coil current value to the control device 45.

In fig. 4, a half-bridge drive circuit is shown, but the present invention is not limited thereto. The inverter circuit 23 may be a so-called full-bridge inverter having two branches in which two switching elements are connected in series.

(working)

Next, the operation of the induction heating cooker in embodiment 1 will be described.

Fig. 5 is a flowchart showing a heating operation of the induction heating cooker of embodiment 1.

Hereinafter, the heating operation of induction heating cooker 100 will be described based on the steps in fig. 5.

When the user places the object 5 on the heating port and instructs the operation display unit 43 to start heating (input of heating power), the control device 45 starts the heating operation.

The control device 45 sets the first shutter 61 to the open state to set the inner coil 111 to the conductive state, and sets the second shutter 62 to the closed state to set the outer coil 112 to the non-conductive state (step S1). When the inner coil 111 is in the conductive state and the outer coil 112 is in the non-conductive state, the load determination unit 46 determines the presence or absence and the material of the object 5 above the inner coil 111 (step S2).

Fig. 6 is a load determination characteristic diagram based on the relationship between the coil current and the input current in the induction heating cooker according to embodiment 1.

As shown in fig. 6, the relationship between the coil current and the input current differs depending on the presence or absence of a load placed above each of the inner coil 111 and the outer coil 112 and the material. The control device 45 stores in advance a load determination table in which the relationship between the coil current and the input current shown in fig. 6 is tabulated in the memory 48.

In the load determination operation of step S2, the control device 45 drives the inverter circuit 23 with a specific drive signal for load determination, and detects the input current from the output signal of the input current detection means 25 a. At the same time, the controller 45 detects the coil current based on the output signal of the coil current detection member 25 b. The load determination unit 46 of the control device 45 determines the presence or absence and the material of the load placed above the coil based on the detected coil current and input current and a load determination table showing the relationship in fig. 6. In this way, the load determination unit 46 of the control device 45 determines the presence or absence and the material of the object 5 placed above each coil based on the correlation (correlation) between the input current and the coil current.

Here, the material of the object 5 to be heated serving as a load is roughly classified into a magnetic material such as iron or ferritic stainless steel (SUS430), and a non-magnetic material such as aluminum or copper. Further, there is a composite body in which a magnetic body is attached to a nonmagnetic body in the object 5 to be heated.

Fig. 7 is a diagram showing an object to be heated of the composite body induction-heated by the induction heating cooker of embodiment 1. Fig. 7 is a view of the object 5 as viewed from the bottom.

As shown in fig. 7, the object 5 to be heated of the composite body is formed by attaching a magnetic body 6 such as stainless steel to the center of the bottom of a non-magnetic pan made of aluminum or the like, for example. The magnetic body 6 can be attached to the non-magnetic body by any method such as adhesion, welding, thermal spraying, pressure bonding, fitting, caulking, embedding, or the like.

In general, the magnetic body 6 is attached to the central portion of the object 5 to be heated, which is a non-magnetic body base and has a flat bottom surface, and the magnetic body 6 is not attached to the outer peripheral portion of the curved bottom surface. When such an object 5 to be heated is placed on the heating port, the magnetic body and the nonmagnetic body are placed above the plurality of heating coils. That is, in the load determination, as shown in fig. 6, the load characteristic of the coil in which the magnetic body and the nonmagnetic body are placed above becomes a characteristic of a "composite region" which is a region between the characteristic of the magnetic body and the characteristic of the nonmagnetic body.

The load determination unit 46 determines that the load placed above each coil is the material of the load directly above each coil. For example, in the object 5 to be heated of the composite shown in fig. 7, the magnetic body 6 is placed directly above the inner peripheral coil 111, and a non-magnetic body serving as a base of the object 5 to be heated is placed further above the magnetic body 6. In this case, the load determination unit 46 determines that the material of the load placed above the inner coil 111 is a magnetic material.

Reference is again made to fig. 5. After step S2, the controller 45 determines the presence or absence of the object 5 above the inner peripheral coil 111 based on the determination result of the load determination unit 46 (step S3). If the object 5 is not located above the inner peripheral coil 111, the controller 45 stops the operation of the drive circuit 50 (step S4). That is, when there is no object 5 above the inner peripheral coil 111, the controller 45 does not determine the presence or absence and the material of the object 5 above the outer peripheral coil 112, and ends the load determination operation.

When there is the object 5 above the inner peripheral coil 111, the controller 45 determines the material of the object 5 above the inner peripheral coil 111 based on the determination result of the load determination unit 46 (step S5). When the material of the object 5 above the inner peripheral coil 111 is a non-magnetic material, the controller 45 stops the operation of the drive circuit 50 (step S4). That is, when the object 5 to be heated made of a non-magnetic material is placed above the inner peripheral coil 111, the control device 45 determines that the object 5 is a load unsuitable for induction heating, and ends the load determination operation without determining the presence or absence and material quality of the object 5 to be heated above the outer peripheral coil 112.

On the other hand, when the material of the object 5 above the inner circumferential coil 111 is a magnetic material, the controller 45 sets the first opening/closing member 61 to the closed state to set the inner circumferential coil 111 to the non-conductive state, and sets the second opening/closing member 62 to the open state to set the outer circumferential coil 112 to the conductive state (step S6). When the inner coil 111 is in the non-conductive state and the outer coil 112 is in the conductive state, the load determination unit 46 determines the presence or absence and the material of the object 5 above the outer coil 112 (step S7).

Next, the controller 45 determines whether or not the object 5 is present above the outer periphery coil 112 or whether the material of the object 5 includes a magnetic material or a non-magnetic material, based on the determination result of the load determination unit 46 (step S8). When the load characteristic is a composite region, controller 45 determines that the material of object 5 is a material containing a non-magnetic substance.

When the material of the object 5 above the outer peripheral coil 112 includes a non-magnetic material, the control device 45 determines that the object 5 is a composite body, and performs the heating operation of the object 5 by the composite body heating operation described later (step S9). When the object 5 is not present above the outer peripheral coil 112, the control device 45 determines that the object 5 is a small-diameter magnetic body, and performs the heating operation of the object 5 by the small-diameter heating operation described later (step S10). When the material of the object 5 above the outer circumferential coil 112 is a magnetic material, the control device 45 determines that the object 5 is a magnetic material having a large diameter, and performs the heating operation of the object 5 by the large diameter heating operation described later (step S11).

The details of each of the composite heating operation, the small diameter heating operation, and the large diameter heating operation will be described below.

(Complex heating operation)

Fig. 8 is a diagram showing a heating coil and an object to be heated in the induction heating cooker according to embodiment 1. Fig. 8 schematically shows a vertical cross section of the composite body with the object 5 placed on the heating port. In fig. 8, only the right side of the center C of the inner and outer coils 111 and 112 is shown, and the top plate 4 is not shown.

As shown in fig. 8, when the object 5 to be heated of the composite body is placed on the heating port of the induction heating cooker 100, the load determination unit 46 determines that the magnetic body is placed above the inner peripheral coil 111 by the above operation. The load determination unit 46 determines that the nonmagnetic material is placed above the outer-peripheral coil 112.

When the material of the object 5 above the inner peripheral coil 111 is a magnetic material and the material of the object 5 above the outer peripheral coil 112 includes a non-magnetic material, the controller 45 performs the following operations as a composite heating operation.

[ preheating mode ]

The preheating mode in the composite heating operation is a heating mode in which the temperature of the object 5 is raised to a preset temperature without putting cooking materials or the like to the object 5. In the preheating mode, the control device 45 heats the outer peripheral portion of the object 5 to be heated, which is emphasized by the composite body.

Here, the heat capacity of the object 5 differs depending on the material. For example, the heat capacity of a nonmagnetic material such as aluminum or copper is smaller than that of a magnetic material such as iron or ferrite stainless steel (SUS 430). Further, the bottom surface of the outer peripheral portion of the object 5 may be curved, the distance between the outer peripheral coil 112 and the object 5 may be further from the central portion of the object 5, and the outer peripheral portion of the object 5 may be less likely to be inductively heated. Therefore, by raising the temperature of the outer peripheral portion of the object 5 before the cooking material or the like is put into the object 5 of the composite, it is possible to suppress variation in the temperature of the object 5 in the normal heating mode described later.

Fig. 9 is a diagram illustrating an operation state of the first opening/closing member and the second opening/closing member in the preheating mode of the induction heating cooker according to embodiment 1.

As shown in fig. 9, the control device 45 sets the first shutter 61 in the closed state and the inner coil 111 in the non-conductive state, and sets the second shutter 62 in the open state and the outer coil 112 in the conductive state. That is, the supply of the high-frequency current to the inner coil 111 is stopped, and the high-frequency current is supplied to the outer coil 112. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to the outer periphery coil 112 to a frequency corresponding to a non-magnetic substance, for example, in the vicinity of 90 kHz.

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to the vicinity of 90 kHz. This inductively heats the outer periphery of the object 5 to be heated of the composite disposed on the top plate 4.

Further, when the mode in which the first opening/closing member 61 is opened and the inner peripheral coil 111 is brought into the conductive state and the second opening/closing member 62 is brought into the closed state and the outer peripheral coil 112 is brought into the non-conductive state is opened in a short time by the control device 45 in a time division manner, the bottom surface temperature of the object 5 to be heated becomes more uniform and more preferable. Alternatively, the bottom surface temperature of the object 5 to be heated may be made more uniform by opening the mode in which the first opening/closing member 61 is turned off, the inner peripheral coil 111 is turned on, the second opening/closing member 62 is turned off, and the outer peripheral coil 112 is also turned on in a time-division manner in a short time by the control device 45.

[ Normal heating mode ]

The normal heating mode in the composite heating operation is a heating mode for heating the entire object 5 in a state where the cooking object or the like is put into the object 5. In the normal heating mode, the controller 45 heats both the central portion and the outer peripheral portion of the object 5 to be heated of the composite body.

The control device 45 alternately repeats the following first operation and second operation. In the first operation, the control device 45 turns the first shutter 61 into the open state, turns the second shutter 62 into the closed state, turns the inner coil 111 into the conductive state, and turns the outer coil 112 into the non-conductive state, and supplies the high-frequency current from the drive circuit 50 to the inner coil 111. In the second operation, the control device 45 sets the first shutter 61 in the closed state, sets the second shutter 62 in the open state, sets the inner coil 111 in the non-conductive state, and sets the outer coil 112 in the conductive state, and supplies the high-frequency current from the drive circuit 50 to the outer coil 112.

The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to the inner coil 111 to a first frequency, and sets the frequency of the high-frequency current supplied from the drive circuit 50 to the outer coil 112 to a second frequency higher than the first frequency. For example, the control device 45 sets the first frequency to a frequency preset in correspondence with the magnetic body, for example, around 25 kHz. Further, for example, the control device 45 sets the second frequency to a frequency corresponding to the non-magnetic substance, for example, in the vicinity of 90 kHz.

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to be in the vicinity of 25kHz or in the vicinity of 90 kHz. This inductively heats the entire object 5 to be heated of the composite disposed on the top plate 4. That is, the normal heating mode is a heating mode in which the amount of power supplied to the inner circumference coil 111 is greater than that in the preheating mode.

The reason why the second frequency of the high-frequency current supplied from the drive circuit 50 to the outer circumferential coil 112 is higher than the first frequency of the high-frequency current supplied to the inner circumferential coil 111 is as follows.

That is, in order to inductively heat a nonmagnetic material made of aluminum or the like, it is necessary to reduce the skin depth (skin depth) of eddy currents generated in the object 5 to be heated, to reduce the penetration volume (penetration volume), and to increase the resistance of the current. Therefore, by supplying a high-frequency current (for example, 80kHz to 100 kHz) to the outer circumferential coil 112 on which the nonmagnetic material is placed, an eddy current of a high frequency is generated in the nonmagnetic material, and the object 5 can be heated by joule heat.

On the other hand, a magnetic body made of iron or the like has a large impedance to eddy current. Therefore, even if a frequency lower than the frequency of the high-frequency current supplied to the outer coil 112 (for example, 20kHz to 35 kHz) is supplied to the inner coil 111 on which the magnetic body is placed, the heating by the joule heat of the object 5 to be heated generated by the eddy current can be sufficiently performed.

Here, when a plurality of induction heating members are driven simultaneously at a plurality of heating ports, noise corresponding to a difference in driving frequency may be generated. In order to suppress such interference sound, the controller 45 may set the second frequency higher than the first frequency by an audible frequency or more (approximately 20kHz or more). Even when the heating operation is performed simultaneously in a plurality of heating ports, the generation of noise can be suppressed.

By such a composite heating operation, induction heating suitable for the material of the object 5 to be heated of the composite can be performed in a configuration in which a high-frequency current is supplied from one drive circuit 50 to the inner circumferential coil 111 and the outer circumferential coil 112. In addition, unevenness in heating temperature when the object 5 of the composite is heated can be suppressed.

(minor diameter heating work)

Fig. 10 is a diagram illustrating an operation state of the first opening/closing member and the second opening/closing member in the small-diameter heating operation of the induction heating cooker according to embodiment 1.

The controller 45 performs the small-diameter heating operation when the object 5 is present above the inner peripheral coil 111 and the object 5 is not present above the outer peripheral coil 112.

As shown in fig. 10, the control device 45 turns the first shutter 61 off to turn the inner coil 111 on, and turns the second shutter 62 on to turn the outer coil 112 off. That is, the control device 45 supplies the high-frequency current from the drive circuit 50 to the inner-circumference coil 111, and stops the supply of the high-frequency current from the drive circuit 50 to the outer-circumference coil 112. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to the inner coil 111 to a frequency corresponding to the magnetic material, for example, around 20 kHz.

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to around 20 kHz. This inductively heats the entire small-diameter object 5 placed on the top plate 4.

By such a small-diameter heating operation, since a high-frequency current is not supplied to the outer circumferential coil 112 on which the object 5 to be heated is not placed, energy can be effectively used. In addition, unnecessary magnetic fields from the outer circumferential coil 112 can be prevented from being radiated.

(major diameter heating work)

Fig. 11 is a diagram illustrating an operation state of the first opening/closing member and the second opening/closing member in the large-diameter heating operation of the induction heating cooker according to embodiment 1.

When the object 5 is present above the inner and outer coils 111 and 112, the controller 45 performs the following operations.

[ Normal heating mode ]

The normal heating mode in the large diameter heating operation is a heating mode for heating the entire large diameter object 5. In the normal heating mode, the control device 45 heats both the central portion and the outer peripheral portion of the large-diameter object 5.

As shown in fig. 11, the control device 45 turns off the first opening/closing member 61 and the second opening/closing member 62 and turns on the inner coil 111 and the outer coil 112, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111 and the outer coil 112. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to the inner circumference coil 111 and the outer circumference coil 112 to a frequency corresponding to the magnetic material, for example, around 20 kHz.

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to around 20 kHz. This inductively heats the entire large-diameter object 5 placed on the top plate 4.

By the large diameter heating operation in the normal heating mode, induction heating suitable for the size and material of the object 5 can be performed.

[ convection mode ]

The convection mode is a cooking mode in which convection is generated in a liquid cooking material contained in the object 5 during cooking such as stewing or cooking.

The control device 45 alternately repeats the following first operation and second operation. In the first operation, the controller 45 sets the inner coil 111 in a conductive state and sets the outer coil 112 in a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111. In the second operation, the controller 45 sets the inner coil 111 in a non-conductive state and sets the outer coil 112 in a conductive state, and supplies a high-frequency current from the drive circuit 50 to the outer coil 112. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to each coil to a frequency corresponding to the magnetic material, for example, around 20 kHz.

By such a large-diameter heating operation in the convection mode, heating of the central portion of the object 5 by the inner circumferential coil 111 and heating of the outer circumferential portion of the object 5 by the outer circumferential coil 112 are alternately repeated. Therefore, convection can be generated in the liquid cooking material such as soup contained in the object to be heated 5, and the liquid cooking material can be spread. That is, in the configuration in which inner coil 111 and outer coil 112 are driven by one drive circuit 50, convection can be generated in the liquid cooking material contained in object to be heated 5.

As described above, embodiment 1 includes a plurality of heating coils, one drive circuit 50 that supplies a high-frequency current to each of the plurality of heating coils, and the opening/closing member 60 that switches each of the plurality of heating coils between a conductive state in which a high-frequency current is supplied from the drive circuit 50 and a non-conductive state in which a high-frequency current is not supplied. Therefore, the circuit configuration can be simplified as compared with a configuration in which the drive circuit 50 is provided for each of the plurality of heating coils. Therefore, the manufacturing cost of induction heating cooker 100 can be reduced. In addition, in the configuration in which the plurality of heating coils are driven by one driving circuit 50, the conduction state and the non-conduction state of each of the plurality of heating coils can be switched.

In embodiment 1, when the inner circumferential coil 111 is in a conductive state and the outer circumferential coil 112 is in a non-conductive state, the controller 45 determines the presence or absence of the object 5 to be heated above the inner circumferential coil 111, and when the object 5 to be heated is not present above the inner circumferential coil 111, stops the operation of the drive circuit 50. Therefore, in the configuration in which the plurality of heating coils are driven by the single driving circuit 50, the load determination operation in the no-load state can be promptly stopped.

Further, the composite heating operation, the small diameter heating operation, or the large diameter heating operation is performed based on the determination results of the material of the object 5 above the inner circumferential coil 111 and the material of the object 5 above the outer circumferential coil 112. Therefore, in the configuration in which the plurality of heating coils are driven by one driving circuit 50, induction heating suitable for the size and material of the object 5 can be performed.

In the heating operation (fig. 5), the following operation may be performed after step S7. The control device 45 turns off both the first opening/closing member 61 and the second opening/closing member 62 and turns on both the inner coil 111 and the outer coil 112. In this state, the load determination unit 46 determines the presence or absence and the material of the object 5 above the inner and outer coils 111 and 112. By increasing such operations, the characteristics of the entire object 5 can be grasped.

(modification 1)

The opening/closing member 60 may be configured to include only one of the first opening/closing member 61 and the second opening/closing member 62. Specific examples are described below.

Fig. 12 is a diagram showing a structure of an opening and closing member in modification 1 of the induction heating cooker of embodiment 1.

As shown in fig. 12, the first opening/closing member 61 may be omitted and only the second opening/closing member 62 may be provided. With such a configuration, the control device 45 can perform the small-diameter heating operation when the object 5 to be heated has a small diameter.

Fig. 13 is a diagram showing a structure of an opening and closing member in modification 1 of the induction heating cooker of embodiment 1.

As shown in fig. 13, the second opening/closing member 62 may be omitted and only the first opening/closing member 61 may be provided. With such a configuration, the controller 45 can perform the complex heating operation in the preheating mode when the object 5 is a complex.

(modification 2)

The inner circumference coil 111 and the outer circumference coil 112 are not limited to circular coils formed concentrically, and may have any shape. The inner and outer coils 111 and 112 are not limited to one coil formed integrally, and may be configured by connecting a plurality of coils in series. Specific examples are described below.

Fig. 14 is a plan view showing the first induction heating member in modification 2 of the induction heating cooker of embodiment 1.

As shown in fig. 14, the first induction heating member 11 has an inner coil 111 disposed at the center of the first induction heating port 1 and an outer coil 112 disposed on the outer periphery side of the inner coil 111.

The inner coil 111 includes a circular coil 111a and a circular coil 111b arranged concentrically. The circular coils 111a and 111b are connected in series. The first opening/closing member 61 is connected in parallel to a series circuit of the circular coils 111a and 111 b. The first opening/closing member 61 switches the circular coils 111a and 111b between a conductive state and a non-conductive state.

The outer circumference coil 112 includes an elliptical coil 112a, an elliptical coil 112b, an elliptical coil 112c, and an elliptical coil 112 d. The elliptical coils 112a to 112d each have an arc shape (banana shape or cucumber shape) of approximately 1/4 in plan view, and are arranged outside the inner circumferential coil 111 so as to substantially follow the outer circumference of the inner circumferential coil 111. The elliptical coils 112a to 112d are connected in series. The second shutter 62 is connected in parallel to the series circuit of the elliptical coils 112a to 112 d. The second opening/closing member 62 switches the elliptical coils 112a to 112d between a conductive state and a non-conductive state. In such a configuration, the heating operation can be performed, and the same effect can be obtained.

The inner and outer coils 111 and 112 may be formed by three or more circular heating coils formed concentrically. That is, the three or more circular heating coils are divided into a heating coil disposed on one part of the inner circumferential side and a heating coil disposed on the other part of the outer circumferential side. The first opening/closing member 61 is connected in parallel to a part of the heating coils on the inner peripheral side among the plurality of heating coils, and is switched between a conductive state and a non-conductive state. The second opening/closing member 62 is connected in parallel to the other heating coil on the outer peripheral side among the plurality of heating coils, and switches between a conductive state and a non-conductive state. In such a configuration, the heating operation can be performed, and the same effect can be obtained.

Embodiment 2.

Hereinafter, the structure and operation of the induction heating cooker in embodiment 2 will be mainly described focusing on differences from embodiment 1. Note that the same components as those in embodiment 1 are denoted by the same reference numerals, and description thereof is omitted.

Fig. 15 is a plan view showing a first induction heating member of an induction heating cooker according to embodiment 2.

As shown in fig. 15, the first induction heating member 11 includes an intermediate coil 113 disposed between an inner circumferential coil 111 and an outer circumferential coil 112. The intermediate coil 113 is formed by winding a wire made of a metal of an insulating coating film. As the lead, for example, any metal such as copper or aluminum can be used. Further, the inner coil 111, the intermediate coil 113, and the outer coil 112 are each independently wound with a conductive wire.

Fig. 16 is a block diagram showing a configuration of an induction heating cooker according to embodiment 2.

As shown in fig. 16, the inner coil 111, the intermediate coil 113, and the outer coil 112 are electrically connected in series. The inner coil 111, the intermediate coil 113, and the outer coil 112 are driven and controlled by one drive circuit 50.

The opening/closing member 60 includes a first opening/closing member 61 connected in parallel to the inner coil 111, a second opening/closing member 62 connected in parallel to the outer coil 112, and a third opening/closing member 63 connected in parallel to the intermediate coil 113. The third opening/closing member 63 switches the intermediate coil 113 between a conductive state in which the high-frequency current is supplied from the drive circuit 50 and a non-conductive state in which the high-frequency current is not supplied. The third opening/closing member 63 is formed of, for example, a relay that opens and closes a contact switch in response to an electric signal or a switching element formed of a semiconductor material. When the intermediate coil 113 is in the on state, a high-frequency current is supplied from the drive circuit 50 to the intermediate coil 113, thereby generating a high-frequency magnetic field from the intermediate coil 113.

Fig. 17 is a diagram showing a circuit configuration of an induction heating cooker according to embodiment 2.

As shown in fig. 17, a resonance circuit including an inner coil 111, an intermediate coil 113, an outer coil 112, and a resonance capacitor 24 is connected to a terminal a and a terminal B which are connection points with the drive circuit 50. The resonance circuit including the inner coil 111, the intermediate coil 113, the outer coil 112, and the resonance capacitor 24 has a resonance frequency corresponding to the inductance of the inner coil 111, the intermediate coil 113, and the outer coil 112 and the capacitance of the resonance capacitor 24. Further, the inductance of the inner coil 111, the intermediate coil 113, and the outer coil 112 changes in accordance with the characteristics of the metal load when the object 5 as the metal load is magnetically coupled, and the resonance frequency of the resonance circuit changes in accordance with the change in the inductance.

With this configuration, a high-frequency current of about several tens of amperes flows through inner coil 111 in the on state. The object 5 to be heated placed on the top plate 4 directly above the inner peripheral coil 111 is inductively heated by high-frequency magnetic flux generated by high-frequency current flowing through the inner peripheral coil 111.

A high-frequency current of about several tens of amperes flows through the intermediate coil 113 in the on state. The object 5 to be heated placed on the top plate 4 directly above the intermediate coil 113 is inductively heated by high-frequency magnetic flux generated by high-frequency current flowing through the intermediate coil 113.

A high-frequency current of about several tens of amperes flows through outer circumferential coil 112 in the on state. The object 5 to be heated placed on the top plate 4 directly above the outer circumferential coil 112 is inductively heated by high-frequency magnetic flux generated by high-frequency current flowing through the outer circumferential coil 112.

(working)

Next, the operation of the induction heating cooker in embodiment 2 will be described.

Fig. 18 and 19 are flowcharts showing the heating operation of the induction heating cooker of embodiment 2.

Hereinafter, the heating operation of induction heating cooker 100 will be described based on the steps in fig. 18 and 19, focusing on the difference from embodiment 1 described above.

The control device 45 turns the first opening/closing member 61 to the open state to turn the inner coil 111 to the conductive state, turns the third opening/closing member 63 to the closed state to turn the intermediate coil 113 to the non-conductive state, and turns the second opening/closing member 62 to the closed state to turn the outer coil 112 to the non-conductive state (step S21). When the inner coil 111 is in the conductive state and the intermediate coil 113 and the outer coil 112 are in the non-conductive state, the load determination unit 46 determines the presence or absence and the material of the object 5 above the inner coil 111 (step S22).

Next, the controller 45 determines the presence or absence of the object 5 above the inner peripheral coil 111 based on the determination result of the load determination unit 46 (step S23). If the object 5 is not located above the inner peripheral coil 111, the controller 45 stops the operation of the drive circuit 50 (step S24). That is, when there is no object 5 to be heated above the inner peripheral coil 111, the controller 45 does not determine the presence or absence and material of the object 5 to be heated above the intermediate coil 113 and the outer peripheral coil 112, and ends the load determination operation.

When there is the object 5 above the inner peripheral coil 111, the controller 45 determines the material of the object 5 above the inner peripheral coil 111 based on the determination result of the load determination unit 46 (step S25). When the material of the object 5 above the inner peripheral coil 111 is a non-magnetic material, the controller 45 stops the operation of the drive circuit 50 (step S24).

On the other hand, when the material of the object 5 above the inner circumferential coil 111 is a magnetic material, the controller 45 closes the first shutter 61 and sets the inner circumferential coil 111 in a non-conductive state. The controller 45 turns the third opening/closing member 63 off to turn the intermediate coil 113 on, and turns the second opening/closing member 62 on to turn the outer-peripheral coil 112 off (step S26). When the inner and outer coils 111 and 112 are in the non-conductive state and the intermediate coil 113 is in the conductive state, the load determination unit 46 determines the presence or absence and the material of the object 5 above the intermediate coil 113 (step S27).

Next, the controller 45 sets the third opening/closing member 63 to the closed state to set the intermediate coil 113 to the non-conductive state, and sets the second opening/closing member 62 to the open state to set the outer-peripheral coil 112 to the conductive state (step S28). When the inner coil 111 and the intermediate coil 113 are in the non-conductive state and the outer coil 112 is in the conductive state, the load determination unit 46 determines the presence or absence and the material of the object 5 above the outer coil 112 (step S29).

Based on the determination result of the load determination unit 46, the control device 45 determines whether or not the object 5 above the intermediate coil 113 is present or not, and whether or not the material of the object 5 includes a magnetic material or a non-magnetic material (step S30).

In step S30, when the material of the object 5 above the intermediate coil 113 includes a non-magnetic substance, the controller 45 determines whether or not the object 5 above the outer peripheral coil 112 is present or not, or whether the material of the object 5 includes a magnetic substance or a non-magnetic substance, based on the determination result of the load determination unit 46 (step S31).

In step S31, when the material of the object 5 above the outer peripheral coil 112 includes a non-magnetic material, the control device 45 determines that the object 5 is a large-diameter composite body, and performs the heating operation of the object 5 by the large-diameter composite body heating operation described later (step S32).

In step S31, when the object 5 is not present above the outer coil 112, the controller 45 determines that the object 5 is a complex of intermediate diameters, and performs the heating operation of the object 5 by the complex heating operation of intermediate diameters to be described later (step S33).

In step S30, when the material of the object 5 above the intermediate coil 113 is a magnetic material, the control device 45 determines whether or not the object 5 above the outer peripheral coil 112 is present, or whether or not the object 5 is a material containing a magnetic material or a non-magnetic material, based on the determination result of the load determination unit 46 (step S34).

In step S34, when the material of the object 5 above the outer peripheral coil 112 is a magnetic material, the control device 45 determines that the object 5 is a magnetic material with a large diameter, and performs the heating operation of the object 5 by the heating operation of the magnetic material with a large diameter (step S35).

In step S34, when the object 5 is not present above the outer coil 112, the controller 45 determines that the object 5 is a magnetic body with a middle diameter, and performs the heating operation of the object 5 by the heating operation of the magnetic body with a middle diameter (described later) (step S36).

In step S30, when the object 5 is not present above the intermediate coil 113, the control device 45 determines that the object 5 is a small-diameter magnetic body, and performs the heating operation of the object 5 by the small-diameter magnetic body heating operation described later (step S37).

The details of each of the heating operations will be described below.

(heating of the Large diameter Complex)

In the composite heating operation of the large diameter, the controller 45 performs a preheating mode for heating the outer peripheral portion of the object 5 to be heated emphasizing the composite and a normal heating mode for heating the entire object 5 to be heated.

[ preheating mode ]

The control device 45 sets the inner coil 111 in a non-conductive state and sets the intermediate coil 113 and the outer coil 112 in a conductive state, and supplies a high-frequency current from the drive circuit 50 to the intermediate coil 113 and the outer coil 112. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to the intermediate coil 113 and the outer-periphery coil 112 to a frequency corresponding to the non-magnetic material, for example, in the vicinity of 90 kHz.

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to the vicinity of 90 kHz. This inductively heats the outer periphery of the object 5 to be heated of the composite disposed on the top plate 4.

In addition, the control device 45 may be configured to open the mode in which the first opening/closing member 61 is in the open state and the inner coil 111 is in the conductive state, and the second opening/closing member 62 and the third opening/closing member 63 are in the closed state and the outer coil 112 and the intermediate coil 113 are in the non-conductive state in a short time in a time division manner. Alternatively, the control device 45 may be configured to open the mode in which all of the first shutter 61, the second shutter 62, and the third shutter 63 are turned off and all of the inner coil 111, the intermediate coil 113, and the outer coil 112 are turned on in a time-division manner in a short time. These operations make it possible to further equalize the temperature of the object 5 to be heated.

[ Normal heating mode ]

The control device 45 alternately repeats the following first operation and second operation. In the first operation, the controller 45 sets the inner coil 111 in a conductive state and sets the intermediate coil 113 and the outer coil 112 in a non-conductive state, and supplies a high-frequency current of a first frequency from the drive circuit 50 to the inner coil 111. In the second operation, the controller 45 sets the inner coil 111 in a non-conductive state and sets the intermediate coil 113 and the outer coil 112 in a conductive state, and supplies a high-frequency current of a second frequency higher than the first frequency from the drive circuit 50 to the intermediate coil 113 and the outer coil 112.

The control device 45 sets the first frequency to a frequency preset in correspondence with the magnetic body, for example, around 25 kHz. Further, for example, the control device 45 sets the second frequency to a frequency corresponding to the non-magnetic substance, for example, in the vicinity of 90 kHz. The control device 45 may set the second frequency to be higher than the first frequency by an audible frequency or more (approximately 20kHz or more).

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to be in the vicinity of 25kHz or in the vicinity of 90 kHz. This inductively heats the entire object 5 to be heated of the composite disposed on the top plate 4.

By such a composite heating operation, induction heating can be performed in a configuration in which a high-frequency current is supplied from one drive circuit 50 to the inner circumferential coil 111, the intermediate coil 113, and the outer circumferential coil 112, in accordance with the material and size of the object 5 to be heated of the composite. In addition, unevenness in heating temperature when the object 5 of the composite is heated can be suppressed.

(Medium diameter Complex heating operation)

In the intermediate-diameter composite heating operation, the controller 45 performs a preheating mode for heating the outer peripheral portion of the object 5 to be heated emphasized by the composite and a normal heating mode for heating the entire object 5 to be heated.

[ preheating mode ]

The control device 45 sets the inner coil 111 and the outer coil 112 in a non-conductive state and sets the intermediate coil 113 in a conductive state, and supplies a high-frequency current from the drive circuit 50 to the intermediate coil 113. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to the intermediate coil 113 to a frequency corresponding to a non-magnetic substance, for example, around 90 kHz.

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to the vicinity of 90 kHz. This inductively heats the outer periphery of the object 5 to be heated of the composite disposed on the top plate 4.

[ Normal heating mode ]

The control device 45 alternately repeats the following first operation and second operation. In the first operation, the controller 45 sets the inner coil 111 in a conductive state and sets the intermediate coil 113 and the outer coil 112 in a non-conductive state, and supplies a high-frequency current of a first frequency from the drive circuit 50 to the inner coil 111. In the second operation, the controller 45 sets the inner coil 111 and the outer coil 112 in the non-conductive state and sets the intermediate coil 113 in the conductive state, and supplies a high-frequency current of a second frequency higher than the first frequency from the drive circuit 50 to the intermediate coil 113.

The control device 45 sets the first frequency to a frequency preset in correspondence with the magnetic body, for example, around 25 kHz. Further, for example, the control device 45 sets the second frequency to a frequency corresponding to the non-magnetic substance, for example, in the vicinity of 90 kHz. The control device 45 may set the second frequency to be higher than the first frequency by an audible frequency or more (approximately 20kHz or more).

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to be in the vicinity of 25kHz or in the vicinity of 90 kHz. This inductively heats the entire object 5 to be heated of the composite disposed on the top plate 4.

By such a composite heating operation, induction heating can be performed in a configuration in which a high-frequency current is supplied from one drive circuit 50 to the inner circumferential coil 111, the intermediate coil 113, and the outer circumferential coil 112, in accordance with the material and size of the object 5 to be heated of the composite. In addition, unevenness in heating temperature when the object 5 of the composite is heated can be suppressed.

(magnetic heating work with a large diameter)

In the large-diameter magnetic substance heating operation, the control device 45 performs a normal heating mode for heating the entire large-diameter object 5 to be heated and a convection mode for causing convection of a liquid cooking material contained in the object 5 to be heated.

[ Normal heating mode ]

The controller 45 turns on the inner coil 111, the intermediate coil 113, and the outer coil 112, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111, the intermediate coil 113, and the outer coil 112. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to each coil to a frequency corresponding to the magnetic material, for example, around 20 kHz.

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to around 20 kHz. This inductively heats the entire large-diameter object 5 placed on the top plate 4.

By such a large-diameter magnetic heating operation in the normal heating mode, induction heating suitable for the size and material of the object 5 can be performed.

[ convection mode ]

The control device 45 turns on some of the heating coils of the inner coil 111, the intermediate coil 113, and the outer coil 112, supplies a high-frequency current from the drive circuit 50, switches the heating coils turned on as time passes, and sequentially changes the heating coils supplying the high-frequency current. Specific examples will be described below while being divided into schemes 1 to 4.

< scheme 1>

The control device 45 alternately repeats the following first operation and second operation. In the first operation, the controller 45 sets the inner coil 111 and the outer coil 112 in a conductive state and sets the intermediate coil 113 in a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111 and the outer coil 112. In the second operation, the controller 45 sets the inner coil 111 in a non-conductive state and sets the intermediate coil 113 and the outer coil 112 in a conductive state, and supplies a high-frequency current from the drive circuit 50 to the intermediate coil 113 and the outer coil 112.

< scheme 2>

The control device 45 sequentially performs the following first operation, second operation, and third operation. In the first operation, the controller 45 sets the inner coil 111 in a conductive state and sets the intermediate coil 113 and the outer coil 112 in a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111. In the second operation, the controller 45 sets the intermediate coil 113 in a conductive state and sets the inner coil 111 and the outer coil 112 in a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the intermediate coil 113. In the third operation, the controller 45 sets the outer coil 112 in a conductive state and sets the inner coil 111 and the intermediate coil 113 in a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the outer coil 112.

< scheme 3>

The control device 45 alternately repeats the following first operation and second operation. In the first operation, the controller 45 sets the inner coil 111 in a conductive state and sets the intermediate coil 113 and the outer coil 112 in a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111. In the second operation, the controller 45 sets the inner coil 111 in a non-conductive state and sets the intermediate coil 113 and the outer coil 112 in a conductive state, and supplies a high-frequency current from the drive circuit 50 to the intermediate coil 113 and the outer coil 112.

< scheme 4>

The control device 45 alternately repeats the following first operation and second operation. In the first operation, the controller 45 sets the inner coil 111 and the outer coil 112 in a non-conductive state and sets the intermediate coil 113 in a conductive state, and supplies a high-frequency current from the drive circuit 50 to the intermediate coil 113. In the second operation, the controller 45 sets the inner coil 111 and the outer coil 112 in a conductive state and sets the intermediate coil 113 in a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111 and the outer coil 112.

In any of claims 1 to 4, the control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to each coil to a frequency corresponding to the magnetic material, for example, around 20 kHz.

By such a heating operation of the large-diameter magnetic body in the convection mode, convection is generated in the liquid cooking material such as soup contained in the object 5 to be heated, and the liquid cooking material can be diffused. That is, in the configuration in which the inner coil 111, the intermediate coil 113, and the outer coil 112 are driven by one driving circuit 50, convection can be generated in the liquid cooking material contained in the heating object 5.

(Medium diameter magnetic heating operation)

In the intermediate-diameter magnetic heating operation, the control device 45 performs a normal heating mode for heating the entire intermediate-diameter object 5 and a convection mode for causing convection of a liquid cooking material contained in the object 5.

[ Normal heating mode ]

The control device 45 turns the inner coil 111 and the intermediate coil 113 into a conductive state and turns the outer coil 112 into a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111 and the intermediate coil 113. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to each coil to a frequency corresponding to the magnetic material, for example, around 20 kHz.

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to around 20 kHz. This inductively heats the entire large-diameter object 5 placed on the top plate 4.

By such a magnetic heating operation of the intermediate diameter in the normal heating mode, induction heating suitable for the size and material of the object 5 can be performed.

[ convection mode ]

The control device 45 alternately repeats the following first operation and second operation. In the first operation, the controller 45 sets the inner coil 111 in a conductive state and sets the intermediate coil 113 and the outer coil 112 in a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111. In the second operation, the controller 45 sets the inner coil 111 and the outer coil 112 in a non-conductive state and sets the intermediate coil 113 in a conductive state, and supplies a high-frequency current from the drive circuit 50 to the intermediate coil 113. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to each coil to a frequency corresponding to the magnetic material, for example, around 20 kHz.

By such a heating operation of the magnetic material having the intermediate diameter in the convection mode, convection is generated in the liquid cooking material such as soup contained in the object 5 to be heated, and the liquid cooking material can be diffused. That is, in the configuration in which the inner coil 111, the intermediate coil 113, and the outer coil 112 are driven by one driving circuit 50, convection can be generated in the liquid cooking material contained in the heating object 5.

(Small diameter magnetic heating work)

The control device 45 sets the inner coil 111 in a conductive state and sets the intermediate coil 113 and the outer coil 112 in a non-conductive state, and supplies a high-frequency current from the drive circuit 50 to the inner coil 111. A high-frequency current is supplied from the drive circuit 50 to the inner-circumference coil 111, and the supply of the high-frequency current from the drive circuit 50 to the intermediate coil 113 and the outer-circumference coil 112 is stopped. The control device 45 sets the frequency of the high-frequency current supplied from the drive circuit 50 to the inner coil 111 to a frequency corresponding to the magnetic material, for example, around 20 kHz.

Then, the control device 45 controls the heating power (electric power) by changing the driving frequency of the switching elements of the inverter circuit 23 to around 20 kHz. This inductively heats the entire small-diameter magnetic object 5 disposed on the top plate 4.

By such a small-diameter magnetic body heating operation, high-frequency current is not supplied to the intermediate coil 113 and the outer circumferential coil 112 on which the object 5 to be heated is not placed, and therefore energy can be effectively used. In addition, unnecessary magnetic fields from the intermediate coil 113 and the outer coil 112 can be prevented from being radiated.

As described above, in embodiment 2, when the inner peripheral coil 111 is in the conductive state and the intermediate coil 113 and the outer peripheral coil 112 are in the non-conductive state, the controller 45 determines the presence or absence of the object 5 above the inner peripheral coil 111, and stops the operation of the drive circuit 50 when the object 5 is not above the inner peripheral coil 111. Therefore, in the configuration in which the plurality of heating coils are driven by the single driving circuit 50, the load detection operation in the no-load state can be promptly stopped.

Further, a heating operation is performed in accordance with the determination result of the presence or absence and material of the object 5 to be heated above each of the inner coil 111, the intermediate coil 113, and the outer coil 112. Therefore, in the configuration in which the plurality of heating coils are driven by one driving circuit 50, induction heating suitable for the size and material of the object 5 can be performed.

(modification 1)

The opening/closing member 60 may be configured by omitting any one of the first opening/closing member 61, the third opening/closing member 63, and the second opening/closing member 62. Specific examples are described below.

Fig. 20 is a diagram showing a structure of an opening and closing member in modification 1 of the induction heating cooker of embodiment 2.

As shown in fig. 20, the first shutter 61 may be omitted and the third shutter 63 and the second shutter 62 may be provided. With such a configuration, when the object 5 is a magnetic body, the control device 45 can perform the above-described magnetic body heating operation of a small diameter, a medium diameter, or a large diameter in accordance with the size of the object 5. Further, when the object 5 to be heated has a middle diameter, the controller 45 can perform the magnetic substance heating operation having the middle diameter. The control device 45 can perform the above-described convection mode in the medium-diameter magnetic substance heating operation or the large-diameter magnetic substance heating operation.

Fig. 21 is a diagram showing a structure of an opening/closing member in modification 1 of the induction heating cooker of embodiment 2.

As shown in fig. 21, the second shutter 62 may be omitted and the first shutter 61 and the third shutter 63 may be provided. With such a configuration, the controller 45 can perform the above-described heating operation of the large-diameter composite when the object 5 to be heated is the large-diameter composite.

(modification 2)

The inner coil 111, the intermediate coil 113, and the outer coil 112 are not limited to circular coils formed concentrically, and may have any shape. The inner coil 111, the intermediate coil 113, and the outer coil 112 are not limited to one coil integrally formed, and may be configured by connecting a plurality of coils in series.

For example, the inner coil 111, the intermediate coil 113, and the outer coil 112 may be formed by four or more circular heating coils formed concentrically. That is, four or more circular heating coils are divided into three heating coil groups on the inner peripheral side, the middle side, and the outer peripheral side. The first opening/closing member 61 is connected in parallel to the heating coil group on the inner peripheral side among the plurality of heating coils, and switches between a conductive state and a non-conductive state. The third opening/closing member 63 is connected in parallel to the center heating coil group among the plurality of heating coils, and switches between a conductive state and a non-conductive state. The second opening/closing member 62 is connected in parallel to the heating coil group on the outer peripheral side among the plurality of heating coils, and switches between a conductive state and a non-conductive state. In such a configuration, the heating operation can be performed, and the same effect can be obtained.

Embodiment 3.

Hereinafter, the structure and operation of the induction heating cooker in embodiment 3 will be mainly described focusing on differences from embodiments 1 and 2 described above. Note that the same components as those in embodiments 1 and 2 are denoted by the same reference numerals, and description thereof is omitted.

Fig. 22 is a diagram showing a circuit configuration of an induction heating cooker according to embodiment 3.

As shown in fig. 22, a resonant circuit including an inner coil 111, an outer coil 112, a resonant capacitor 24a, and a resonant capacitor 24b is connected to the drive circuit 50.

The resonance capacitor 24a is connected in series to the inner coil 111 and the outer coil 112. The resonance capacitor 24b is connected in parallel with the resonance capacitor 24a via the changeover switch 70.

The changeover switch 70 is constituted by, for example, a relay that opens and closes a contact switch in response to an electric signal or a switching element made of a semiconductor material. When the changeover switch 70 is in the closed state, the resonance capacitor 24b is connected in parallel with the resonance capacitor 24 a. When the changeover switch 70 is in the off state, the connection of the resonance capacitor 24b is disconnected. That is, by turning the changeover switch 70 to the closed state, the capacitance of the resonance capacitor forming the resonance circuit together with the inner circumference coil 111 and the outer circumference coil 112 is increased. Further, by turning off the changeover switch 70, the capacitance of the resonance capacitor forming the resonance circuit together with the inner coil 111 and the outer coil 112 is reduced.

(working)

The control device 45 switches the switching switch 70 to change the capacitance of the resonance capacitor in accordance with at least one of the switching of the conductive state and the non-conductive state of the plurality of heating coils and the frequency of the high-frequency current. That is, the control device 45 decreases the capacitance of the resonance capacitor as the number of the heating coils in the on state among the plurality of heating coils increases. Further, the control device 45 decreases the capacitance of the resonance capacitor as the frequency of the high-frequency current increases.

Specific examples of the composite heating operation, the small diameter heating operation, and the large diameter heating operation in embodiment 1 are described below.

(Complex heating operation)

[ preheating mode ]

In the preheating mode in the composite heating operation, the controller 45 turns on the outer periphery coil 112 to heat the outer periphery of the object 5. The control device 45 sets the frequency of the high-frequency current supplied to the outer coil 112 to a frequency corresponding to the non-magnetic material, for example, around 90 kHz.

In this operation, the controller 45 turns off the changeover switch 70 to reduce the capacitance of the resonance capacitor forming the resonance circuit together with the outer circumferential coil 112. This increases the resonance frequency of the resonance circuit, and the resonance frequency can be brought close to the drive frequency of the drive circuit 50, thereby improving the heating efficiency to the outer circumferential coil 112.

[ Normal heating mode ]

In the normal heating mode in the composite heating operation, the controller 45 alternately repeats a first operation of bringing only the inner coil 111 into conduction and a second operation of bringing only the outer coil 112 into conduction. In the first operation, the controller 45 sets the frequency of the high-frequency current supplied to the inner peripheral coil 111 to a frequency corresponding to the magnetic material, for example, around 25 kHz. In the second operation, the controller 45 sets the frequency of the high-frequency current supplied to the outer coil 112 to a frequency corresponding to the non-magnetic material, for example, around 90 kHz.

In this operation, the controller 45 turns the changeover switch 70 to the closed state in the first operation, and increases the capacitance of the resonance capacitor forming the resonance circuit together with the inner circumferential coil 111. In the second operation, the controller 45 turns off the changeover switch 70 to reduce the capacitance of the resonance capacitor forming the resonance circuit together with the outer circumferential coil 112. Accordingly, in both the first operation and the second operation, the resonance frequency can be made close to the driving frequency of the driving circuit 50, and the heating efficiency to the inner coil 111 and the outer coil 112 can be improved.

(minor diameter heating work)

In the small-diameter heating operation, the controller 45 turns on only the inner coil 111. The control device 45 sets the frequency of the high-frequency current supplied to the inner peripheral coil 111 to a frequency corresponding to the magnetic material, for example, around 20 kHz.

In this operation, the controller 45 closes the changeover switch 70 to increase the capacitance of the resonance capacitor forming the resonance circuit together with the inner circumferential coil 111. Since only the inner coil 111 is turned on and the inductance of the resonance circuit is reduced, the capacitance of the resonance capacitor is increased, so that the resonance frequency of the resonance circuit is not greatly changed by the load. This can bring the resonance frequency close to the drive frequency of the drive circuit 50, thereby improving the heating efficiency to the inner coil 111.

(major diameter heating work)

[ Normal heating mode ]

In the normal heating mode during the large diameter heating operation, the controller 45 brings the inner coil 111 and the outer coil 112 into a conductive state. The control device 45 sets the frequency of the high-frequency current supplied to the inner coil 111 and the outer coil 112 to a frequency corresponding to the magnetic material, for example, around 20 kHz.

In this operation, the controller 45 turns off the changeover switch 70 to reduce the capacitance of the resonance capacitor forming the resonance circuit together with the inner and outer coils 111 and 112. Since the inner coil 111 and the outer coil 112 are in a conductive state and the inductance of the resonance circuit increases, the capacitance of the resonance capacitor is reduced, so that the resonance frequency of the resonance circuit does not change greatly due to the load. This can bring the resonance frequency close to the drive frequency of the drive circuit 50, and can improve the heating efficiency to the inner and outer coils 111 and 112.

[ convection mode ]

In the convection mode in the large diameter heating operation, the controller 45 alternately repeats a first operation of bringing only the inner coil 111 into a conduction state and a second operation of bringing only the outer coil 112 into a conduction state. The control device 45 sets the frequency of the high-frequency current supplied to the inner coil 111 and the outer coil 112 to a frequency corresponding to the magnetic material, for example, around 20 kHz.

In this operation, the controller 45 turns the changeover switch 70 to the closed state in both the first operation and the second operation, and increases the capacitance of the resonance capacitor that forms the resonance circuit together with the inner coil 111 or the outer coil 112. Since only one of the inner coil 111 and the outer coil 112 is turned on, the inductance of the resonance circuit is reduced, and therefore, the capacitance of the resonance capacitor is increased, so that the resonance frequency of the resonance circuit is not largely changed by the load. This can bring the resonance frequency close to the drive frequency of the drive circuit 50, and can improve the heating efficiency to the inner and outer coils 111 and 112.

In embodiment 3, a configuration in which two resonance capacitors are provided in a resonance circuit is described, but three or more resonance capacitors may be provided. Further, a plurality of resonance capacitors may be connected in series, and a switching means for short-circuiting at least one resonance capacitor may be provided to vary the capacitance of the resonance capacitor. Further, a part of the plurality of resonance capacitors may be connected in series and connected in parallel with another part of the resonance capacitors.

In embodiment 3, a configuration including two heating coils, i.e., the inner coil 111 and the outer coil 112, has been described, but the number of heating coils is not limited to this. For example, the structure of the resonant capacitor of embodiment 3 may be applied to the structure of embodiment 2.

Description of reference numerals

1a first induction heating port, 2a second induction heating port, 3a third induction heating port, 4a top plate, 5 an object to be heated, 6 a magnetic body, 11a first induction heating member, 12a second induction heating member, 13 a third induction heating member, 21 an ac power supply, 22a dc power supply circuit, 22a diode bridge, 22b reactor, 22c smoothing capacitor, 23 inverter circuit, 23a IGBT, 23b IGBT, 23c diode, 23d diode, 24 resonant capacitor, 24a resonant capacitor, 24b resonant capacitor, 25a input current detecting member, 25b coil current detecting member, 40 operating portion, 40a operating portion, 40b operating portion, 40c operating portion, 41 display portion, 41a display portion, 41b display portion, 41c display portion, 43 operating display portion, 45 control device, 46 load determination portion, 48 memory, 50 drive circuit, 60 shutter, 61 first shutter, 62 second shutter, 63 third shutter, 70 switch, 100 induction heating cooker, 111 inner circumference coil, 111a circular coil, 111b circular coil, 112 outer circumference coil, 112a elliptical coil, 112b elliptical coil, 112c elliptical coil, 112d elliptical coil, 113 middle coil.

Claims (25)

1. An induction heating cooker comprising: a plurality of heating coils, the plurality of heating coils including an inner peripheral coil arranged on the innermost peripheral side and an outer peripheral coil arranged on the outermost peripheral side; a drive circuit that supplies a high frequency current to each of the plurality of heating coils; an opening and closing member that switches each of the plurality of heating coils between a conduction state in which the high-frequency current is supplied from the drive circuit and a non-conduction state in which the high-frequency current is not supplied ;as well as a control device that controls the operation of the drive circuit and the opening/closing member, The control device determines the presence or absence of an object to be heated above the inner coil when the inner coil is in a conductive state and the outer coil is in a non-conductive state, When there is no object to be heated above the inner peripheral coil, the operation of the drive circuit is stopped. 2. The induction heating cooker according to claim 1, wherein, The control device determines the presence or absence and material of the object to be heated above the inner coil when the inner coil is in a conducting state and the outer coil is in a non-conducting state, When the object to be heated is located above the inner peripheral coil, when the inner peripheral coil is in a non-conductive state and the outer peripheral coil is in a conductive state, it is determined that the above-mentioned outer peripheral coil is in a conductive state. The presence or absence of the object to be heated and its material. 3. The induction heating cooker according to claim 2, wherein: When the material of the object to be heated above the inner circumferential coil is a magnetic body and the material of the object to be heated above the outer circumferential coil includes a non-magnetic body, the control device assigns the inner The peripheral coil is in a non-conductive state, the outer peripheral coil is in a conductive state, and the high-frequency current is supplied from the drive circuit to the outer peripheral coil. 4. The induction heating cooker according to claim 2, wherein: When the material of the object to be heated above the inner circumferential coil is a magnetic body and the material of the object to be heated above the outer circumferential coil includes a non-magnetic body, the control device alternately repeats : an operation of supplying the high-frequency current of a first frequency to the inner coil from the drive circuit by setting the inner coil to be in a conductive state and the outer coil to a non-conductive state; and The inner peripheral coil is set to a non-conductive state, the outer peripheral coil is set to a conductive state, and the high frequency of a second frequency higher than the first frequency is supplied from the drive circuit to the outer peripheral coil frequency current operation. 5. The induction heating cooker according to claim 2, wherein, When the object to be heated is located above the inner circumference coil and the object to be heated is not located above the outer circumference coil, the control device sets the inner circumference coil in a conductive state and the The outer peripheral coil is in a non-conductive state, and the high-frequency current is supplied from the drive circuit to the inner peripheral coil. 6. The induction heating cooker according to claim 2, wherein, When the object to be heated is located above the inner coil and the outer coil, the control device sets the inner coil and the outer coil to be in a conductive state, and sends the information from the drive circuit to the heating target. The high-frequency current is supplied to the inner coil and the outer coil. 7. The induction heating cooker according to claim 2, wherein, When the object to be heated is located above the inner coil and the outer coil, the control device alternately repeats: an operation of supplying the high-frequency current from the drive circuit to the inner coil by placing the inner coil in a conductive state and the outer coil in a non-conducting state; and An operation of supplying the high-frequency current from the drive circuit to the outer peripheral coil by setting the inner peripheral coil in a non-conductive state and in the outer peripheral coil in a conductive state. 8. The induction heating cooker according to any one of claims 1 to 7, wherein The control device determines the material of the object to be heated above the inner coil when the inner coil is in a conducting state and the outer coil is in a non-conducting state, When the material of the object to be heated above the inner peripheral coil is a non-magnetic body, the operation of the drive circuit is stopped. 9. The induction heating cooker according to claim 1, wherein, The plurality of heating coils include intermediate coils disposed between the inner coils and the outer coils, The control device determines the presence or absence of the object to be heated above the inner coil when the inner coil is in a conductive state and the intermediate coil and the outer coil are in a non-conduction state, When there is no object to be heated above the inner peripheral coil, the operation of the drive circuit is stopped. 10. The induction heating cooker according to claim 9, wherein, The control device determines the presence or absence and material of the object to be heated above the inner coil when the inner coil is in a conductive state and the intermediate coil and the outer coil are in a non-conduction state , When there is the object to be heated above the inner coil, When the inner coil and the outer coil are in a non-conductive state and the intermediate coil is in a conductive state, the presence or absence and the material of the object to be heated above the intermediate coil are determined, When the inner coil and the intermediate coil are in a non-conductive state and the outer coil is in a conductive state, the presence or absence and material of the object to be heated above the outer coil are determined. 11. The induction heating cooker according to claim 10, wherein, In the control device, when the material of the object to be heated above the inner coil is a magnetic body and the material of the object to be heated above the intermediate coil and the outer coil includes a non-magnetic body the inner coil is in a non-conductive state, the intermediate coil and the outer coil are in a conductive state, and the high frequency is supplied from the drive circuit to the intermediate coil and the outer coil current. 12. The induction heating cooker according to claim 10, wherein, In the control device, when the material of the object to be heated above the inner coil is a magnetic body and the material of the object to be heated above the intermediate coil and the outer coil includes a non-magnetic body , alternately repeat: The inner coil is turned on, the intermediate coil and the outer coil are turned off, and the high-frequency current of the first frequency is supplied from the drive circuit to the inner coil work; and The inner coil is in a non-conductive state, the intermediate coil and the outer coil are in a conductive state, and the intermediate coil and the outer coil are supplied from the drive circuit with a ratio of power higher than that of the first coil. The high frequency current of the second frequency with high frequency works. 13. The induction heating cooker according to claim 10, wherein, In the control device, the material of the object to be heated above the inner coil is a magnetic body, the material of the object to be heated above the intermediate coil includes a non-magnetic body, and the material above the outer coil is not In the case of the object to be heated, the inner coil and the outer coil are in a non-conductive state, the intermediate coil is in a conductive state, and the intermediate coil is supplied from the drive circuit. the high-frequency current. 14. The induction heating cooker according to claim 10, wherein, The control device turns on the inner coil when the object to be heated is located above the inner coil and the object to be heated is not located above the intermediate coil and the outer coil. The intermediate coil and the outer coil are in a non-conductive state, and the high-frequency current is supplied from the drive circuit to the inner coil. 15. The induction heating cooker according to claim 10, wherein, When the object to be heated is located above the inner coil, the intermediate coil, and the outer coil, the control device sets the inner coil, the intermediate coil, and the outer coil as In the ON state, the high-frequency current is supplied from the drive circuit to the inner coil, the intermediate coil, and the outer coil. 16. The induction heating cooker according to claim 10, wherein, When the object to be heated is located above the inner coil, the intermediate coil, and the outer coil, the control device controls the inner coil, the intermediate coil, and the outer coil to set the object to be heated. Part of the heating coils are turned on, and the high-frequency current from the drive circuit is supplied, As time elapses, the heating coils that are in an on state are switched to sequentially change the heating coils to which the high-frequency current is supplied. 17. The induction heating cooker of claim 10, wherein: When the object to be heated is located above the inner coil and the intermediate coil, and the object to be heated is not located above the outer coil, the control device controls the inner coil and the intermediate coil. The coil is in a conductive state, the outer coil is in a non-conduction state, and the high-frequency current is supplied from the drive circuit to the inner coil and the intermediate coil. 18. The induction heating cooker according to claim 10, wherein, When the object to be heated is located above the inner peripheral coil and the intermediate coil and the object to be heated is not located above the outer peripheral coil, the control device alternately repeats: an operation of supplying the high-frequency current from the drive circuit to the inner coil by placing the inner coil in a conductive state and the intermediate coil and the outer coil in a non-conducting state; and An operation of supplying the high-frequency current from the drive circuit to the intermediate coil by placing the inner coil and the outer coil in a non-conducting state, and placing the intermediate coil in a conducting state. 19. The induction heating cooker according to any one of claims 1 to 18, wherein The drive circuit includes a resonant capacitor, and the resonant capacitor and the plurality of heating coils form a resonant circuit and are configured to have variable capacitance, The control device varies the capacitance of the resonance capacitor according to at least one of switching between the conduction state and the non-conduction state of the plurality of heating coils and the frequency of the high-frequency current. 20. The induction heating cooker according to claim 19, wherein, The greater the number of the heating coils in the conductive state among the plurality of the heating coils, the more the control device reduces the capacitance of the resonance capacitor. 21. The induction heating cooker according to claim 19 or 20, wherein, The higher the frequency of the high-frequency current, the more the control device reduces the capacitance of the resonance capacitor. 22. The induction heating cooker according to any one of claims 1 to 21, wherein The induction heating cooker includes: an input current detection part that detects an input current to the drive circuit; and a coil current detection part that detects a coil current flowing in the heating coil, The control device determines the presence or absence and material of the object to be heated above the heating coil based on the correlation between the input current and the coil current. 23. The induction heating cooker according to any one of claims 1 to 22, wherein The drive circuit has an inverter circuit having at least one branch formed by connecting two switching elements in series. 24. The induction heating cooker according to claim 23, wherein, The switching element is formed using a wide band gap semiconductor material. 25. The induction heating cooker according to any one of claims 1 to 24, wherein The opening and closing member is formed of a semiconductor material.

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